John Kelly served in the United States Merchant Marine while he was a teenager. At 20, he enlisted in the U.S. Marine Corps and commanded forces in Iraq between 2003 and 2009. It's safe to say there are few challenges he cannot meet.

That said, President Donald Trump is a completely different animal. And Kelly — as the president's newly named Chief of Staff — will certainly have his hands full.

It's important that he succeed. If he doesn't, today's instability could become tomorrow's disaster.

Kelly wasted no time asserting his authority, showing White House Communications Director, Anthony Scaramucci, the door before Kelly's formal start date of Aug. 15. Kelly also put a stop to the revolving door that led into the Oval Office while Reince Priebus was Chief of Staff.

During Priebus's tenure, people lingered outside the oval office, and Trump would wave them in without an appointment. Kelly made clear to staff, including Jared Kushner and Ivanka Trump, that all visits to the President would go through him.

This isn't about testosterone. It's about bringing order to a flailing administration.

The question is whether Kelly can get Trump to apply some of that discipline to himself. Getting the staff under control reduces the chance of backbiting, leaks and general friction. The President, however, is the key driver of whether he succeeds or fails. With an overall job approval under 39 percent, it is critical Trump take Kelly's advice and find ways to focus less on trivial issues and more on important ones.

On Monday morning, Trump threw caution to the wind. In a series of early morning tweets, the president attacked polling data and the media.

We all should want Kelly to succeed. While it's easy to criticize the likes of Scaramucci, Sean Spicer, and Steve Bannon, what if the better appointees like James Mattis at Defense, H.R. McMaster at National Security and Nikki Haley at the United Nations were to get fed up and quit? They are from the more level-headed wing of the administration and Trump — America! — needs them to exert their influence.

If Trump continues to obsess over silly issues — perceived slights from members of Congress, distracting fights with the media, dismissing demonstrably true facts as fake and fiction — some of the good people might not stick around. If you're Mattis and your Commander-In-Chief is too distracted with exacting revenge against people on Twitter instead of focusing on national defense, would you stay?

Some reports say Kelly and Trump have been conferring on tweets before the president sends them off. Perhaps that's a step in the right direction. But Kelly can't always be in the room with Trump.

It's early in Kelly's tenure. We're rooting for him to extend his influence beyond who meets with the president and bring about real change in the administration.